Carbonization of cellulose acetate eibers with gaseous hci and swelling agent to separate from wool fibers



Patented Sept. 4, 1951 CARBONIZATION F CELLU'LOSE ACETATE FIBERS WITH GASEOUS HG] AND SWELL- ING AGENT T0 SEPARATE FROM WOOL FIBERS Alan 'Crummett, Leeds, and Albert Mellor, Spondon, near Derby, England, assignors to Gelanese Corporation of America, a corporation of Delaware No Drawing. Application June 22, 1948, Serial No. 34,544. In Great Britain July 10, 1947 1 Claim. 1

This invention relates to the removal of unwanted fibres of cellulose derivatives from a product containing wool and especially to the recovery of Wool from material containing it in association with other fibres.

Cellulose fibres, for example cotton and regenerated cellulose fibres, can be removed from mixtures thereof with wool, for example waste textile material containing wool in association with cellulose fibres, by carbonising processes involving the treatment of the material with various acid substances so as to bring the cellulose fibres into a friable form but to leave the wool substantially unaffected. The friable cellulose fibres can then readily be separated from the wool fibres by mechanical means. One way of effecting the acid treatment is to subject the material to the action of vapours of hydrochloric acid at say 50-100 C.

Such treatments, however, are not capable of rendering fibres of cellulose acetate readily removable under conditions which leave the wool in a fit state for further use. Cellulose acetate seems to be very much less readily attacked and degraded by acids than is cellulose itself.

According to the present invention cellulose acetate fibres in admixture with wool are brought to a friable and readily removable form by the action of the vapour of hydro chloric acid in the presence of a swelling agent for the cellulose acetate. By this treatment it is possible to render friable and easily removable not only the cellulose acetate fibres but also any cellulose fibres which may be present.

The treatment can be effected at temperatures of 50 to 100 C.

The swelling agent may be present in the material prior to the contacting of the material with the hydrochloric acid vapour; for instance the material may be moistened with the swelling agent either as such or in the form of an aqueous or other solution or the material may be subjected to the action of vapours of a swelling agent so as to permit the cellulose acetate fibres to take up the swelling agent. Preferably, however, a volatile swelling agent is employed and the vapours thereof are brought into contact with the material in admixture with the hydrochloric acid vapour.

Examples of swelling agents which can be employed for the purposes of the present invention are acetone, methyl ethyl ketone, diacetone alcohol, dioxane, glycol monoalkyl ethers, e. g. glycol monoethyl or methyl ether, and lower fatty acids for example acetic acid, formic or propionic acid. When the swelling agent is to be used in the form of vapour for the treatment of the material it is advantageously one of which the vapour is taken up by the cellulose acetate fibres at the temperature employed for the treatment with the inorganic acid vapours: for example, acetone may be employed at temperatures of 50-60" C. and acetic acid at temperatures of 50-100 C.

It is convenient to vaporize the hydrochloric acid and the volatile swelling agent and to pass the mixture of vapours into a mass of the material to be treated. The action of the acid vapour and swelling agent should be continued until examination of a sample of the material shows that the cellulose acetate fibre content has been rendered sufilciently friable to permit ready removal by mechanical means. The removal of the friable cellulose acetate from the material, which has been treated with the vapours, can be effected by, for instance, shaking, sifting, suction or like means or by any convenient combination of these. Finally the material remaining may be washed and thereafter dried. It is then substantially free from cellulose or cellulose ester fibres.

The treatment can be effected with the: aid of the apparatus commonly employed for the carbonising of waste woollen material with vapours of hydrochloric acid. Such apparatus usually comprises a horizontal, perforated, drum for containing a charge of the material to be treated. The drum is enclosed by a suitable casing and is rotatable upon a hollow live axle through which hot or cold gases e. g. hot furnace gases, or vapours of hydrochloric acid from a vapouriser. can be fed to the interior of the drum. In some forms of carbonisers the vapouriser consists of an extension of the hollow axle of the drum provided with heating means and means for slowly introducing concentrated hydrochloric acid. The casing is provided with openings for discharge of gases or vapours and both the casing and the drum with doors to permit charging and discharging of the drum.

In operating the new process a charge of the material to be treated, may be placed in the perforated drum of a carbonising machine of the kind indicated above. The drum is then set in rotation and hot air or hot furnace gases are led through it, via the hollow axle, for the purpose of warming the material and bringing it into a substantially dry state should it have been wet at the time of loading into the machine. A mixture of concentrated hydrochloric acid and volatile swelling agent, for example acetic acid, is then vaporised in the vaporisor provided. The rate of introduction of the liquid into the vaporisor can conveniently serve to control the rate of supply of acid vapours to the material. When inspection of a sample of the material shows that the cellulose acetate content has been rendered friable and easily separated mechanically from the wool the passage of the acid vapours is discontinued and acid vapour remaining in the drum flushed out by means of warm air or furnace gases. Owing to the sifting action of the rotating perforated drum much of the cellulose acetate and cellulose content of the material falls away and out of the drum, collecting in the base of the casing surrounding the drum. The contents of the drum are then subjected to a suitable shaking and/or other treatment to remove remaining friable cellulose acetate or cellulose and are finally washed and dried.

As an indication of the duration of the treatment and the proportion of acid required in relation to the material treated, it may be mentioned that satisfactory carbonisation of the cellulose and cellulose acetate in a charge of 6 cWt. of rags containing 50% of wool, and 25% of cellulose acetate fibres, the remaining fibres being cellulose can be effected in two to three hours by means of about 120 lbs. of a mixture of concentrated hydrochloric with either glacial acetic acid or 85% formic acid, the mixture containing about 75% of the hydrochloric acid. The temperature of the material may be 80 to 100 C.

The material treated in accordance with the invention may consist, for instance, of waste yarn, tailors fabric cuttings or Woollen rags. It may be of a kind in which wool and cellulose acetate fibres, or cellulose fibres if present, are in very close association as in the case of yarns spun from a mixture of wool with cellulose acetate staple fibre.

Though the process of the invention is particuiarly useful for the recovery of wool from waste material containing it, it may be also used for other purposes, for examplefor the removal of small proportions of cellulose acetate fibre from a woven or knitted fabric.

The invention has been described more particularly with reference to cellulose acetate as the cellulose ester or other fibre to be removed from the wool. The new process can, however,

'to the action of the vapors produced by vaporizing a mixture consisting of concentrated hydrochloric acid and glacial acetic acid, said mixture containing about of hydrochloric acid, at'a temperature of -100 C. until the cellulose acetate fibres have been rendered friable and thereafter'separating the wool fibres from the friable residue.

ALAN CRUMMETL ALBERT MELLOR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 981,574 Knoevenagel Jan. 10, 1911 1,818,505 Rivat et al Aug. 11, 1931. 1,980,191 Dickie et al Nov. 13, 1934 2,152,640 Ferguson Apr. 4, 1939 2,276,173 Ferguson Mar. 10, 1942. 2,393,712 Seymour et al Jan. 29, 1946 FOREIGN PATENTS Number Country Date Great Britain Sept. 17, 1928 

